Submission #212052

#	Time	Username	Problem	Language	Result	Execution time	Memory
212052		VietnameseEagle	Building 4 (JOI20_building4)	C++14	100 / 100	419 ms	84588 KiB

building4

#include<bits/stdc++.h>
using namespace std;
#define int long long
#define forinc(i,a,b) for(int i=a;i<=b;++i)
#define fordec(i,a,b) for(int i=a;i>=b;--i)
#define fi first
#define se second
#define pii pair<int,int>

const int maxn=5e5+10;
int n,a[2*maxn],b[2*maxn];
int L[2*maxn][3],R[2*maxn][3];
vector<char> kq;
bool chq(int u,int l,int r)
{
    return u>=l&&u<=r;
}
main()
{
    //freopen("test.inp","r",stdin);
    ios_base::sync_with_stdio(false);
    cin>>n;
    forinc(i,1,2*n) cin>>a[i];
    forinc(i,1,2*n) cin>>b[i];
    forinc(i,1,2*n+5) forinc(j,0,1) L[i][j]=INT_MAX;
    forinc(i,1,2*n+5) forinc(j,0,1) R[i][j]=INT_MIN;
    L[1][0]=0,L[1][1]=1;
    R[1][0]=0,R[1][1]=1;
    forinc(i,2,2*n) forinc(t,0,1)
    {
        if(t==0){
            if(L[i-1][0]!=INT_MAX&&a[i]>=a[i-1]) L[i][t]=min(L[i][t],L[i-1][0]);
            if(L[i-1][1]!=INT_MAX&&a[i]>=b[i-1]) L[i][t]=min(L[i][t],L[i-1][1]);

            if(R[i-1][0]!=INT_MIN&&a[i]>=a[i-1]) R[i][t]=max(R[i][t],R[i-1][0]);
            if(R[i-1][1]!=INT_MIN&&a[i]>=b[i-1]) R[i][t]=max(R[i][t],R[i-1][1]);
        }
        else{
            if(L[i-1][0]!=INT_MAX&&b[i]>=a[i-1]) L[i][t]=min(L[i][t],L[i-1][0]+1);
            if(L[i-1][1]!=INT_MAX&&b[i]>=b[i-1]) L[i][t]=min(L[i][t],L[i-1][1]+1);

            if(R[i-1][0]!=INT_MIN&&b[i]>=a[i-1]) R[i][t]=max(R[i][t],R[i-1][0]+1);
            if(R[i-1][1]!=INT_MIN&&b[i]>=b[i-1]) R[i][t]=max(R[i][t],R[i-1][1]+1);
        }
    }
    if(!chq(n,L[2*n][0],R[2*n][0])&&!chq(n,L[2*n][1],R[2*n][1])) return cout<<-1,0;
    int c=(chq(n,L[2*n][0],R[2*n][0])?0:1);
    kq.push_back((char)('A'+c));
    int cur=(c==0?n:n-1);
  //  cout<<L[5][1]<<" "<<R[5][1];
   // return 0;
    fordec(i,2*n-1,1)
    {
        bool ok=0;
        if(chq(cur,L[i][0],R[i][0]))
        {
            int tmp=(c==0?a[i+1]:b[i+1]);
            if(a[i]<=tmp)
            {
             //   cout<<i<<" "<<1<<"\n";
                kq.push_back('A');
                c=0;
                ok=1;
            }
        }
        if(chq(cur,L[i][1],R[i][1])&&ok==0){
            int tmp=(c==0?a[i+1]:b[i+1]);
       //     cout<<i;
         //   return 0;
            if(b[i]<=tmp)
            {
              //  cout<<i<<" "<<2<<"\n";
                kq.push_back('B');
                c=1;
                cur--;
            }
        }
    }
    reverse(kq.begin(),kq.end());
    for(auto &v:kq) cout<<v;
}

Compilation message (stderr)

building4.cpp:18:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
 main()
      ^

• Subtask 1: 11 / 11
• Subtask 2: 89 / 89